This invention relates generally to operating systems and particularly to initializing and restarting those operating systems, for example, after power is initially turned on or after a crash has occurred.
When a computer system is initially turned on, a basic input/output system or "BIOS" begins to operate. The BIOS controls many important functions of the personal computer, such as how it interprets key strokes, how it puts characters on the screen, and how it communicates with other devices. The BIOS typically instructs the computer to test itself every time the user turns the computer on. To do this, the BIOS uses a power on self test or "POST".
When the personal computer starts, it typically first enters what is called the "real mode". The computer accesses a special memory location holding program instructions including a jump instruction pointing to the BIOS code. Initially, the BIOS instructs the system microprocessor to run through components of the system and determine whether they are operating properly. Next, any expansion boards which have been installed are checked, and thereafter, the microprocessor begins the actual bootup process. During the bootup process, the BIOS code may instruct the microprocessor to jump to a section of code instructing the microprocessor how to read the first sector of the system floppy, hard disk or CD-ROM drive. The microprocessor then loads the operating system to start actual computer operations.
The Windows.RTM. operating system is perhaps the most common operating system used in personal computers. It is an "open" system in that it is adaptable to different computer systems and it is adaptable to changing hardware on any given computer system. At least, in part, due to this openness, it takes a considerable amount of time for the Windows.RTM. operating system to start up. To some users, this delay may be an annoyance and, in some instances, the start up process may interfere with the way a system operates.
For example, set top personal computers are personal computers associated with television systems which combine television capabilities, both analog and digital, and computer capabilities, such as internet access. It is expected that users of set top personal computers will consider those computers to be akin to normal electronic appliances. Thus, the users may not be willing to accommodate delays in initiation or error messages on their television screens. For example, a user might simultaneously, in a picture-within-picture system, play a game running on the Windows.RTM. operating system and simultaneously watch television. If the game were to crash, an error message could appear on the screen which would interfere with normal television viewing and at least for a short period, the television picture would be affected by the computer crash.
In substantially all cases, users would benefit by a quicker initiation of program operations. This could occur in at least three areas. Initially, when the computer turns on, it would be desirable to begin operations as quickly as possible. Secondly, when a program error or crash occurs, it would be desirable to restart the computer as soon as possible. Similarly, when a variety of issues come up during the course of computer operation, some users may desire to simply restart the computer to avoid dealing with and identifying the source of the problem.
Current computer systems have some capabilities to speed the initiation of the computer system. For example, it is known to use a "fast on" capability which bypasses all or part of the POST routine. Similarly, some laptop computers have a suspend/resume operation. When desired, the user can press a suspend button and all the settings on the computer are stored. When the computer powers up thereafter, the computer recognizes that a suspend had occurred and immediately resumes operations exactly where the computer left off before. In addition, some computer systems work in an "always on" mode whereby it is never necessary, absent a problem, to reboot the computer system. For example, Windows.RTM. 98 will have an Advanced Configuration and Power Interface (ACPI) function which is akin to a computer system which is never turned off. Some simple computer systems, such as personal data assistants (PDAs), use what is known as a Real Time Operating System (RTOS) to allow the computer to start quickly.
None of the techniques described above help when a program has crashed. In each of these cases at least a substantial part of the startup operation must be re-done after a crash. This can result in substantial delay and it is an impediment to creating a seamless appearance to the system user. Thus, there is a continuing need for methods that enable operating systems to initiate and restart more quickly, for example, after a crash or when initially turned on particularly with open operating systems. Similarly in connection with specialized computer systems, such as a set top personal computer, it would be desirable make normal computer operations invisible to the user.